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<p class="Decl"><span class="EmptyRef">procedure</span> BeginMeasuring(<span class="EmptyRef">const</span> Callback: <a href="../../../Types/TAreaChangedEvent.htm">TAreaChangedEvent</a>);</p>
<h2>Description</h2>
<p class="Body">Attaches a callback method to the <a href="../Events/OnAreaChanged.htm">OnAreaChanged</a> event and switches the bitmap into <a href="../../../../../Additional Topics/Repaint Optimization.htm#MeasuringMode">measuring mode</a>. The  event handler previously attached to the <a href="../Events/OnAreaChanged.htm">OnAreaChanged</a> event is preserved and will be reset once measuring is stopped by calling <a href="EndMeasuring.htm">EndMeasuring</a>. </p>
<p id="hidden">[See also]: <a href="EndMeasuring.htm">EndMeasuring</a></p>
<p class="Body">&nbsp;</p>
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